Variable frequency drive and method of its air cooling

ABSTRACT

Variable frequency drive and method of its air cooling relates to the field of electrical engineering, in particular, to the fields of frequency drive (FD) and converter technology with a forced double-circuit air cooling system and designed for using in sealed cabinet structures. The first air circuit formed by loop air moving around each of local modules 3; 4 of the sealed compartment with using the circulation fan 26. Describes special structure of local modules 3; 4 allows to perform the cooling air barrier between the cabinet enclosure and each local module of the sealed compartment with using the internal air channel 18.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present patent application claims priority to Ukrainian patent application a201906697 filed Jun. 14, 2019.

FIELD OF THE INVENTION

The claimed invention relates to the field of electrical engineering, in particular, to the fields of frequency drive (FD) and converter technology with a forced air cooling system and designed for using in medium-voltage/high-voltage frequency drives and other electrical devices cabinet structures.

BACKGROUND OF THE INVENTION Description of the Related Art

Currently known methods and systems for air cooling of high-voltage electrical equipment. Such equipment emitting significant dissipated energy in the form of heat. Prior art air cooling systems designed for removing a generated heat through both natural and forced ventilation methods.

Forced air cooling systems usually made in a form of a sealed enclosure with a double-circuit cooling system, wherein the internal circuit is sealed and connected to the external ventilated circuit through a heat exchanger.

Depending on the type of used refrigerant types of cooling systems, for example liquid, air or mixed. Each of used methods has its own advantages and disadvantages depending on operating conditions.

The air forced cooling system is one of the most common, due to the relative simplicity of design and ease of use. The main task in the development of this area of technology is the designing of sealed cabinet with reduced dimensions, simplified the structure, increased maintainability and operational characteristics.

Patent application WO2013064211 sets out a test container (10, 40, 70), which includes like a rectangular parallelepiped the container (12, 42, 72), disposed therein electrical components (14, 16, 90, 94, 96) of the transformer checking system, which in the test mode are like the corresponding heat source, and a cooling system, at least with one heat exchanger (18, 20, 44, 46, 114), there is a moving device (22, 24, 48, 49) by means of which, at at least one heat exchanger (18, 20, 44, 46, 114) can move from a transport position inside the container (12, 42, 72) to the operating position, which is located at least partially outside the container (12, 42, 72).

Providing a test area system and thus, test area system components for testing of high-voltage transformers, that make possible a particularly simple transportation, assembly and disassembly of the test area system and prevent the use of the rotating converter.

The disadvantages of the described invention include the increasing dimensions in the operating conditions and the presence of flexible connection of heat exchangers could lead to their failure and violation of the tightness of the circuit.

Utility model patent RU144730 sets out a method for cooling of transformer compartment of a high-voltage electrical device, where used four tangential fans are installed in the lower part of the multi-winding transformer cabinet. Three axial fans are installed on the doors of the multi-winding transformer cabinet, which provide cooling air into the cabinet.

The disadvantages of the described technical solutions include a large number of fans, which leads increasing of dimensions of the device.

Also, in the prior art, patent U.S. Pat. No. 9,545,037B2 sets out systems and methods for cooling electric drives wherein an enclosure forming two or more sealed compartments, wherein each of the two or more sealed compartments prevents external air outside of the two or more sealed compartments from entering the two or more sealed compartments. Two or more air-to-air heat exchangers adjacent to a respective one of the two or more sealed compartments. Wherein the air-to-air heat exchangers cooling internal air within each of sealed compartments without allowing entering the external air. Wherein a duct which is adjacent to the sealed compartments, wherein air-to-air heat exchangers are positioned within the duct. Wherein the external air flows through the duct and through each of air-to-air heat exchangers. wherein the duct has at least one wall in common with the two or more sealed compartments, wherein sealed compartments are positioned in thermal contact with the at least one common wall. Wherein each of said heat exchangers further comprising a plurality of plates.

The disadvantages of the described method include the scheme of air flow moving, according to which a heated air enters to the heat exchangers after the radiator, thereby reducing the efficiency of the heat exchanger and cooling system at all.

Patent CN203416157(U) OT 29 Jan. 2014 sets out a device for medium and high voltage frequency converters with a circulation cooling system. The device is made in a monoblock case and comprising power and low-current electronic components placed in at least one sealed compartment with a double-circuit forced air cooling system with at least one air heat exchanger.

Wherein a method of forced air cooling comprising:

performing of a circulation channel,

implementation of forced air circulation through heat exchangers. A first heat exchange is carried out in the internal circuit of the frequency converter, then a second heat exchange is carried out through the heat exchanger. The heat exchanger contains three independent channels, namely: a heat exchange channel, a cold air channel and a hot air channel.

The disadvantages of the described invention include a separation of air flow into two parts inside the compartment, which leads to use an additional recirculation fan inside the compartment to obtain an air flow of sufficient density with a required flow rate and speed. Using a heat exchanger with a three level heat exchange could reduce the efficiency of the heat exchanger.

The claimed technical solution aims solving a technical problems, of prior art.

SUMMARY OF THE INVENTION

A technical result, achieved from implementation of the claimed invention lies in improving of maintainability, as well as increasing of ergonomic characteristics of the sealed compartment of a variable frequency drive (VFD) with increased efficiency dual-circuit forced air cooling system.

The variable frequency drive comprising:

a cabinet with a double-circuit forced air cooling system, a power and low-current electronic components, a control unit. Wherein said cabinet contains sealed and ventilated compartments. Wherein said sealed compartment comprising a first air circuit, local modules with a power and low-current electronic components. Wherein the ventilated compartment comprising a second air circuit.

Said first air circuit and second air circuit are designed in thermal communication via a number of air heat exchangers installed within the ventilated compartment. The first air circuit arranged within the sealed compartment and configured as an internal air channel which is formed around of a perimeter of each local module of sealed compartment and equipped with a circulation fan.

Said internal air channel connected to the number of air heat exchangers. Wherein each pair of said number of air heat exchangers is equipped with the circulation fan.

The Second air circuit contains straight air channels arranged within the ventilated compartment adjacent to the sealed compartment, wherein each of said straight air channels comprising one pair of the air heat exchangers with a blast fan between them.

A method of air cooling of variable frequency drive based on described structure comprising:

performing a double-circuit forced air cooling system; arranging a first air cooling circuit within a sealed compartment of a variable frequency drive cabinet; arranging a second air cooling circuit within a ventilated compartment of the variable frequency drive cabinet; separating the sealed compartment by local modules with a power and low-current electronic components; performing an internal air channels around of a perimeter of each local module of the sealed compartment, performing a cooling air barrier between the cabinet enclosure and each local module of the sealed compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—illustrates a general view of the cabinet of variable frequency drive;

FIG. 2—illustrates a side view of the cabinet of VFD;

FIG. 3—illustrates a transformer module of VFD;

FIG. 4—illustrates a back side view of the cabinet of VFD;

FIG. 5—illustrates double-circuit forced air cooling system;

FIG. 6—illustrates air heat exchangers positioning;

FIG. 7—illustrates an air heat exchanger structure;

The variable frequency drive (FIG. 1), is made in a monoblock design cabinet in a form of a rectangular parallelepiped with openings for doors, sealed terminal chambers and assembly covers of cooling system elements. The cabinet enclosure 1 is divided into a length by two compartments with power and low-current electronic components and a control unit. The cabinet 1 is designed with a double-circuit forced air cooling system.

One of said compartments is sealed 2 and comprising a first air circuit (an internal cooling circuit) and local modules 3; 4 (FIG. 2) with the power and low-current electronic components.

Local module 3 is designed for transformer. Wherein a transformer 6 (FIG. 3) is installed on a movable frame 5. According to present invention the transformer 6 could be designed as dry-type transformer, also it could be another well known type of transformer.

The movable frame 5 comprising a roller base 7 with a guiding ways 8. Described structure allows removing the transformer 6 out of the cabinet 1 during a maintenance.

One of side walls 9 of the cabinet is equipped with a assembly cover 10 of the transformer 6 for servicing the transformer and access to the internal air channel 18 of the local module 3.

In an operation condition, the assembly cover 10 is hermetically closed. A sealed terminal chamber 11 for external connections is installed above the assembly cover 10. Said terminal chamber 11 also could be made in a form of a separate modular switching cell.

The local module 4 comprising a number of power cells 12 (FIG. 2) of the VFD wherein said power cells are installed on an electrically secured frame made of polymer material. Also said power cells designed for using bypass switching devices. For example, mechanical switch device based on vacuum chamber, for example high operated communication device (HOpCoD).

An access to the local module 4 realized through sealed doors 13 (FIG. 1) installed on the front side of the cabinet.

Wherein another side (back side) illustrated in (FIG. 4) of the cabinet comprising a sealed terminal chamber 15 and assembly covers 16 of the cooling system elements, such as fans 26; 27 and heat exchangers 22.

The specified design allows increasing maintainability and ease of use of the VFD.

According to the variant of variable frequency drive implementation the control unit cased in a separate module 17 (FIG. 2) which installed between two adjacent local modules 3; 4 of the sealed compartment 2 within the internal air channel. The control unit module 17 has a part designed in a trapezoidal shape, which is ventilated from three sides. Said trapezoidal shaped part of control unit module 17 installed on the direction of cooling air within the sealed compartment 2.

Walls of trapezoidal shaped part of control unit module 17 allow installation of law current electronic components of control unit as well as integrated microprocessor controller 33 (FIG. 1). The walls of trapezoidal shaped part of control unit module 17 serve as radiators for law current electronic components.

Described design allows performing an efficient cooling of the control unit without using additional fans and radiators.

The first air circuit arranged within the sealed compartment 2 configured as an internal air channel 18 (FIG. 5) which is formed around of a perimeter of the each local module 3; 4 of the sealed compartment 2. Wherein the internal air channel 18 connected to the number of air heat exchangers 22 and formed as an air barrier between the cabinet enclosure 1 and each local module 3; 4 of the sealed compartment 2. Said air barrier formed by a cooling air 19 of the first air circuit 32 and allows to protect internal power and law-current electronic components against influence of external high temperature.

The internal air channel 18 of the sealed compartment 2 contains thermoelectric devices with additional radiators 20 (FIG. 6) of air dehumidification system. Said thermoelectric devices designed for removing moisture out off the sealed compartment without violating a tightness of the sealed compartment.

Radiators 20 (FIG. 6) installed within the second air circuit on direction of external air flow 21.

The air dehumidification system also could be equipped with additional electric air heaters (not shown in the drawings) installed within the sealed compartment 2.

The internal air channel 18 connected to the number of air heat exchangers 22. According to the present implementation of the invention the sealed compartment comprising at least two adjacent local modules 3; 4.

Each of local module 3; 4 comprising at least two pairs of air heat exchangers 22 (FIG. 6 and FIG. 7). Said air heat exchangers 22 installed within a vented straight air channels 23, arranged within the ventilated compartment 24 (FIG. 1) adjacent to the sealed compartment 2. Both of said straight air channels 23 and air heat exchangers 22 forming the second air circuit (an external cooling circuit).

Each pair of said number of air heat exchangers 22 is equipped with at least one fan. Wherein first pair 22.1 of heat exchangers is equipped with a circulation fan 26. Said circulation fan 26 integrated into the first air circuit. Wherein at least one circulation fan 26 is installed within a sealed air channel 28 arranged between the heat exchangers 22 of first pair 22.1. Also at least one circulation fan 26 is aligned with air ways of each pair 22.1 of said number of air heat exchangers 22.

A second pair 22.2 of air heat exchangers is equipped with a blast fan 27 between them. Said blast fan 27 integrated into the second air circuit and arranged within straight air channels 23 as well as the second pair 22.2 of air heat exchangers.

Each of heat exchangers 22 consists of laminated sandwiched plates 29 (FIG. 7). Said laminated sandwiched plates 29 comprising metal plates with a polymer sandwiched layer between them. Wherein the laminated sandwiched plates 29 separated by spacing elements 30 installed periodically and connected by coupling rods 31 installed around the perimeter of the heat exchanger 22.

Each of heat exchangers 22 contains at least two separated air ways, one of which is orthogonal to another, wherein said two air ways configured between three neighboring laminated sandwiched plates 29. Said spacing elements 30 forming the orthogonal air ways without mixing air flows of first and second air circuits.

The straight air channels 23 (Fig.) are equipped with vents 31.

A method of forced air cooling of sealed compartment of the VFD according to present invention directly depends on described structure of the VFD and could be implemented by using features of the invention with achieving of said technical result.

According to the present method the system of forced air cooling of sealed compartment of the VFD designed with a double air circuits. Wherein the first circuit 32 is sealed and designed as the internal cooling circuit of the sealed compartment 2. The sealed compartment 2 of the VFD designed according to the class IP58 or NEMA 4. The second air circuit 25 designed within the ventilated compartment 24 of the variable frequency drive cabinet 1 and forming the external cooling circuit.

The first and second air cooling circuits are designed in thermal communication via a number of air heat exchangers 22 installed within the ventilated compartment 24.

The first air circuit 32 forming by loop air moving around and through of each of local modules 3; 4 of the sealed compartment with using the circulation fan 26. Describes special structure of local modules 3; 4 allows to perform the cooling air barrier between the cabinet enclosure and each local module of the sealed compartment within the internal air channel 18.

During the operation of VFD controlling air fans capacity via the control unit module 17 depending on temperature within the sealed compartment or each of local modules which measured by sensors 14.

Also, before start of VFD detecting an air humidity inside of the sealed compartment 2 and draining the air by its heating until the moisture is collecting on thermoelectric devices installed in the internal air channels 18. After that, removing collected moisture out off the sealed compartment without violating a tightness of the sealed compartment.

Control of internal equipment of the VFD is implemented on the basis of a programmable microprocessor controller 33 installed in the control unit module 17. The control unit module 17, cased in the separate trapezoidal housing within the air channel 18, between the modules 3; 4 of the sealed compartment 2.

The claimed invention allows to the achieve of the specified benefits and advantages, with providing optimal dimensions and tightness of the VFD, improving ergonomics, as well as effectiveness of forced air cooling of electronic components placed within the sealed compartment with protection against moisture and dust according to the standard not lower than NEMA 4 or IP58, by special structure of integrated dual-circuit air cooling system. 

What is claimed is:
 1. A variable frequency drive comprising: a cabinet with a double-circuit forced air cooling system, a power and low-current electronic components, a control unit; wherein said cabinet contains sealed and ventilated compartments, wherein said sealed compartment comprising a first air circuit, local modules with a power and low-current electronic components, wherein said ventilated compartment comprising a second air circuit, wherein said first air circuit and second air circuit are designed in thermal communication via a number of air heat exchangers installed within the ventilated compartment, wherein the first air circuit arranged within the sealed compartment within an internal air channel which is formed around of a perimeter of local module of sealed compartment and equipped with a circulation fan,  wherein the internal air channel connected to the number of air heat exchangers and formed as an air barrier between the cabinet enclosure and each local module of the sealed compartment;  wherein each pair of said number of air heat exchangers is equipped with the circulation fan, wherein the second air circuit contains straight air channels arranged within the ventilated compartment adjacent to the sealed compartment, wherein each of said straight air channels comprising one pair of the air heat exchangers with a blast fan between them.
 2. The variable frequency drive of claim 1 wherein the cabinet designed with four-sided access, wherein a front side of the cabinet is equipped with sealed doors of each local module of sealed compartment, as well as control unit module with integrated microprocessor controller, wherein one of said local modules of the sealed compartment contains a transformer, wherein one of said local modules of the sealed compartment contains a number of power cells, wherein other sides of the cabinet comprising a sealed terminal chamber and assembly covers of the cooling system elements, such as fans and heat exchangers.
 3. The variable frequency drive of claim 1 wherein one of side walls of the cabinet is equipped with the transformer assembly cover for servicing the transformer and access to the internal air channel.
 4. The variable frequency drive of claim 1 wherein at least one circulation fan installed within a sealed air channel arranged between the number of heat exchangers, wherein at least on circulation fan aligned with air ways of each pair of said number of air heat exchangers.
 5. The variable frequency drive of claim 1 wherein each of heat exchangers consists of laminated sandwiched plates comprising metal plates with a polymer sandwiched layer between them, wherein the laminated sandwiched plates divided by spacing elements installed periodically and connected by coupling rods installed around of the perimeter of the heat exchanger.
 6. The variable frequency drive of claim 1 wherein each of heat exchangers contains at least two divided air ways, one of which is orthogonal to another, wherein said two air ways configured between three neighboring laminated sandwiched plates.
 7. The variable frequency drive of claim 1 wherein the control unit cased in a separate module and installed between two adjacent local modules of sealed compartment within the internal air channel.
 8. A method of air cooling of variable frequency drive comprising: performing a double-circuit forced air cooling system; arranging a first air cooling circuit within a sealed compartment of a variable frequency drive cabinet; arranging a second air cooling circuit within a ventilated compartment of the variable frequency drive cabinet; wherein said first and second air cooling circuit are designed in thermal communication via a number of air heat exchangers installed within the ventilated compartment; dividing the sealed compartment by local modules with a power and low-current electronic components; performing an internal air channels around of a perimeter of each local module of the sealed compartment, wherein each local module is equipped with at least one a circulation fan; performing a loop air moving within each of local modules with using the circulation fan, and performing a cooling air barrier between the cabinet enclosure and each local module of the sealed compartment; directing an air loop of each local module through the number of air heat exchangers, installing the number of air heat exchangers in pairs within a straight air flow channels arranged within the ventilated compartment adjacent to the sealed compartment, wherein each of said straight air flow channels comprising one pair of the air heat exchangers with a blast fan between them.
 9. The method of air cooling of variable frequency drive of claim 8 wherein controlling air fans capacity via a control unit depending on temperature within the sealed cabinet or each of local modules.
 10. The method of air cooling of variable frequency drive of claim 8 wherein detecting an air humidity inside of the sealed compartment, draining the air by heating until the moisture collecting on thermoelectric devices installed in the internal air channels, removing the moisture out off the sealed compartment without violating a tightness of the sealed compartment. 